Form field overtypes instead of allowing for a correction/change

I created a simple Adobe form and one of my testers noted that when he incorrectly typed his email address, he couldn't backspace over it or delete it. He tried typing over it and just got typed copy over typed copy like this:

See how the "y" in Ruby is darker? You can type directly over the same letter and it gets darker, but if you try to delete an incorrect entry and type over, it doubles up the typing.